Chapter B, Problem B.26P

Interpretation Introduction

(a)

Interpretation:

The structure for $\text{2-chloropropene}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{2-chloropropene}$ is:

Explanation of Solution

The given molecule is $\text{2-chloropropene}$

In this molecule, the root is propene. Thus, the longest carbon chain must have three carbon atoms. The suffix ‘ene’ indicates that there is a double bond in the chain. The position of the double bond in the chain is between carbon atoms C1 and C2.

The root can be shown as:

At C2 carbon atom of the root, one chlorine is attached. Thus, the structure of $\text{2-chloropropene}$ is:

Conclusion

The structure of $\text{2-chloropropene}$ is as shown above.

Interpretation Introduction

(b)

Interpretation:

The structure for $\text{3-methylbut-1-ene}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene, if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{3-methylbut-1-ene}$ is:

Explanation of Solution

The given molecule is $\text{3-methylbut-1-ene}$

In this molecule, the root is butene. Thus, the longest carbon chain must have four carbon atoms. The suffix ‘ene’ indicates that there is a double bond in the chain. The position of the double bond in the chain is between carbon atoms C1 and C2.

The root can be shown as:

At C3 carbon atom of the root, a methyl substituent is attached.

Thus, the structure of $\text{3-methylbut-1-ene}$ is:

Conclusion

The structure of $\text{3-methylbut-1-ene}$ is as shown above.

Interpretation Introduction

(c)

Interpretation:

The structure for $\text{2, 3-dimethyl-2-butene}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene, if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{2, 3-dimethyl-2-butene}$ is:

Explanation of Solution

The given molecule is $\text{2, 3-dimethyl-2-butene}$

In this molecule, the root is butene. Thus, the longest carbon chain must have four carbon atoms. The suffix ‘ene’ indicates that there is a double bond in the chain. The position of the double bond in the chain is between carbon atoms C2 and C3.

The root can be shown as:

At C2 and C3 carbon atoms of the root, two methyl substituents are attached.

Thus, the structure of $\text{2, 3-dimethyl-2-butene}$ is:

Conclusion

The structure of $\text{2, 3-dimethyl-2-butene}$ is as shown above.

Interpretation Introduction

(d)

Interpretation:

The structure for $\text{2-ethoxy-3, 3-dimethylcyclohexene}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene, if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents, are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{2-ethoxy-3, 3-dimethylcyclohexene}$ is:

Explanation of Solution

The given molecule is $\text{2-ethoxy-3, 3-dimethylcyclohexene}$

In this molecule, the root is cyclohexene. Thus, the largest carbon ring must have six carbon atoms. The suffix ‘ene’ indicates that there is a double bond in the ring. The position of the double bond in the ring is always between carbon atoms C1 and C2.

The root can be shown as:

At C2 and C3 carbon atoms of the ring, one ethoxy and two methyl substituents are attached respectively. Thus, the structure of $\text{2-ethoxy-3, 3-dimethylcyclohexene}$ is:

Conclusion

The structure of $\text{2-ethoxy-3, 3-dimethylcyclohexene}$ is as shown above.

Interpretation Introduction

(e)

Interpretation:

The structure for $\text{3, 4, 5-trimethoxycycloheptene}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene, if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{3, 4, 5-trimethoxycycloheptene}$ is:

Explanation of Solution

The given molecule is $\text{3, 4, 5-trimethoxycycloheptene}$

In this molecule, the root is cyclohexene. Thus, the largest carbon ring must have seven carbon atoms. The suffix ‘ene’ indicates that there is a double bond in the ring. The position of the double bond in the ring is always between carbon atoms C1 and C2.

The root can be shown as:

At C2, C3, and C4 carbon atoms of this ring, three methoxy substituents are attached.

Thus, the structure of $\text{3, 4, 5-trimethoxycycloheptene}$ is:

Conclusion

The structure of $\text{3, 4, 5-trimethoxycycloheptene}$ is as shown above.

Interpretation Introduction

(f)

Interpretation:

The structure for $\text{3-bromo-2-methyl-4-nitrocyclopentene}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene, if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{3-bromo-2-methyl-4-nitrocyclopentene}$ is:

Explanation of Solution

The given molecule is $\text{3-bromo-2-methyl-4-nitrocyclopentene}$

In this molecule, the root is cyclohexene. Thus, the largest carbon ring must have six carbon atoms. The suffix ‘ene’ indicates that there is a double bond in the ring. The position of the double bond in the ring is always between carbon atoms C1 and C2.

The root can be shown as:

At C2, C3, and C4 carbon atoms, bromine, methyl, and nitro group are attached.

Thus, the structure of $\text{3-bromo-2-methyl-4-nitrocyclopentene}$ is:

Conclusion

The structure of $\text{3-bromo-2-methyl-4-nitrocyclopentene}$ is as shown above.

Interpretation Introduction

(g)

Interpretation:

The structure for $\text{3, 3-dibromo-4-methylcyclopentene}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene, if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{3, 3-dibromo-4-methylcyclopentene}$ is:

Explanation of Solution

The given molecule is $\text{3, 3-dibromo-4-methylcyclopentene}$

In this molecule, the root is cyclopentene. Thus, the largest carbon ring must have five carbon atoms. The suffix ‘ene’ indicates that there is a double bond in the ring. The position of the double bond in the ring is always between carbon atoms C1 and C2.

The root can be shown as:

At C3 and C4 carbon atoms of the ring, two bromine atoms and one methyl group are attached.

Thus, the structure of $\text{3, 3-dibromo-4-methylcyclopentene}$ is:

Conclusion

The structure of $\text{3, 3-dibromo-4-methylcyclopentene}$ is as shown above.

Interpretation Introduction

(h)

Interpretation:

The structure for $\text{4-methyl-2-pentyne}$ is to be drawn.

Concept introduction:

In case of molecules containing a $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond, the longest continuous carbon chain or largest ring that contains the double or triple bond is considered as the root. The root is named from the name of the analogous alkane or cycloalkane by replacing the suffix ane by ene, if a double bond is present. The suffix ane is replaced by yne if a triple bond is present.

If the root is a chain, numbering begins from that end of the chain which encounters the $\text{C=C }$ or $\text{C}\equiv \text{C}$ bond at the earliest. If there is a tie, the chain is numbered such that the substituents get the lowest locator numbers.

The carbon atoms having a double or triple bond between them are always assigned C1 and C2, if the root is a ring. This must be done such that the locator numbers for the substituents are minimized. The lower of the two locator numbers for the $\text{C=C }$ or $\text{C}\equiv \text{C}$ is written before the ene or yne suffix. Prefixes and locator numbers are used for the substituents attached. For more than two different substituents, alphabetical order is followed.

Answer to Problem B.26P

The structure for $\text{4-methyl-2-pentyne}$ is:

Explanation of Solution

The given molecule is $\text{4-methyl-2-pentyne}$

In this molecule, the root is pentyne. Thus, the longest carbon chain must have five carbon atoms. The suffix ‘yne’ indicates that there is a triple bond in the chain. The position of the triple bond in the chain is always between carbon atoms C2 and C3.

The root can be shown as:

At C4 carbon atom of the root, a methyl group is attached.

Thus, the structure of $\text{4-methyl-2-pentyne}$ is:

Conclusion

The structure of $\text{2-ethoxy-3, 3-dimethylcyclohexene}$ is as shown above.